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Calixarene tool kit can read epigenetic codes.

A group of researchers at the University of Victoria has demonstrated that calixarene molecules can be used to read information encoded on DNA-packaging proteins called histones. The discovery provides a new tool for the emerging field of epigenetics, the study of heritable information stored in molecules other than DNA and RNA.

In the past, histones were thought of as spools around which DNA was wound. More recently, post-translational modifications to the histones--for example, acetylation or methylation of certain amino acids--have been shown to play a role in determining which genes get expressed at which times. This epigenetic 'histone code' can be probed by antibodies in enzyme-linked immunosorbent assays (ELISAs). But such assays have shortcomings. "Some code elements are really similar and difficult to distinguish," says Fraser Hof, professor of chemistry at the University of Victoria, noting that the failure rate with antibodies is over 20 per cent.

Hofs group has been working on an alternative approach based on calixarenes. These cup-shaped macromolecules bind preferentially to certain histone code elements. In a paper recently published in the Journal of the American Chemical Society, Hofs group described a new assay in which various calixarenes, each paired with a fluorescent dye, were exposed to peptides bearing the modifications of the histone code. The dyes were quenched by binding to the calixarenes, but histone code elements compete for the binding site. Since each calixarene has a different affinity for a given code element, a pattern of fluorescent responses results. Taken together, the signals lead to a unique 'fingerprint' for each code element.


A set of only three calixarenes was sufficient to distinguish histone code elements with a high degree of reproducibility. "We really didn't expect this to work so well; I thought we were going to need up to 10 different sensors," says Hof. Even better, the system works in real time, unlike ELISA. The team hopes it can be used to study the activity of the enzymes that add and remove histone code elements.
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Title Annotation:TECHNIQUES
Publication:Canadian Chemical News
Date:Sep 1, 2012
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